When is chlorine demand considered satisfied?

Chlorine demand is considered satisfied when the reaction of chlorine with organic and inorganic materials stops. This signifies that all available substances that react with chlorine, such as pathogens, organic matter, and other oxidizable materials, have been effectively neutralized or reduced in concentration. Once this residual chlorine demand is satisfied, any additional chlorine will remain in the water and can serve as a disinfecting agent.

While it may seem logical to consider chlorine demand satisfied when all bacteria are killed or when there is no chlorine left in the system, these interpretations do not capture the full context of chlorine demand. The primary focus is on the consumption of chlorine due to reactions with various constituents in the water rather than just the eradication of pathogens or the complete depletion of chlorine. The acceptable taste of water does not provide a direct measurement of chlorine demand satisfaction either, as taste can be subjective and influenced by many factors beyond chlorine levels.